Aircraft remote proportional control mechanism



Feb. 16, 1960 F. A. woDAL x-:TAL

AIRCRAFT REMOTE PROPORTIONAL CONTROL MECHANISM 4 Sheets-Sheet l Original Filed Sept. 16. 1948 .5302.0 NIFPOEIP 0.-.

INVENTOR. v/mc/s 6. Woo/Pzgy /Paaspr 5. EHI/Es #5ml/nw 29mm, #2.13m

Feb. 16, 41960 F. A. woDAL ETAL 2,925,234

AIRCRAFT REMOTE PROPORTIONAL CONTROL MECHANISM Original Filed Sept. 16. 1948 4 Sheets-Sheet 2 A D. c. PolTENTmL FREQUENCY MEQ" FREQUENCY FT g. E.

y Y |50 FITCH clRcul-r Feb. 16, 1960 F. A. woDAL ETAL AIRCRAFT REMOTE PROPORTIONAL CONTROL MECHANISM .Original Filed Sept. 16, 1948 4 Sheets-Sheet 3 INVENTOR.

Femm/s 19. h/aam..

BY Kaefer 5 kl/f.:

zfwwnea, {elim} Rowwen 4- Mn/mu Feb. 16, 1960 F. A. woDAL ET Al. 2,925,234

AIRCRAFT REMOTE PROPORTIONAL CONTROL MECHANISM original Filed Sept. 16, 1948 4 Sheets-Sheet 4 1N V EN TOR. FAHNc/s f2 Wop/9L nc. l l

negws HTTORNEYS 2,925,234 "Patented Feb, `161,

ice

w 2,925,234` AmCRAFrnEMoTErnoPoRnoNAL coNr-RoL MECHANISM Francis A. Wodan, Haddbnsels, NJ., and Robert-B.

Eaves, Kretlow, Pa., assgnors, by mesne assignments, to Earle` W. Wallick, Silver Spring, and Temple N. Joyce., Arnold Post Office, Md.

Retiled for abandoned application Serial No. 49,592, September 16, 1948. This application January 5, 1956 SerialNo. 557,593

4 claims. (ci, 244-11) The presen-t invention relates to apparatus for controlling moving vehicles and more particularly to a system through which the control of 'a gyroscope stabilized mobile craft i's enabled from a remote station. The present application is a substitute for abandoned applica# tion'Serial No. 49,592, filed September 16, 1948. The principles of the invention relates to or may be used in the control of land vehicles such as automobiles, tanks, trucks, mine detonatorsand detectors and the like, as well as water craft and torpedoes,` and also airplanes, rotary winged aircraft, missiles, bombs and gliders. However', for purposes of .clarity and conciseness, the descriptions and illustrations of the invention hereinafter set forth will deal with the application of the invention to aircraft control.

It is an object of the present invention to provide novel means for the remote control of aircraft, other craft or vehicles, whereby the attitude and heading o-f the craft may be controlled by air-operator or device locatedfa't a remote point eithero'nV thefgroundor: aboard another craft. Y. i A `Another object of the invention is to provide` means whereby acontrolled craft will assume an attitude or heading in` response to the actuation of suitable remote controlf-elements,` the controlled craft changing its atti tude or heading proportionally in angularfvalues and substantially at the. same rate of movement as any change affected in the remote control elements.

Another object is to provide a control lever and associated `apparatus so that the position of the control lever will be indicative of the attitude of a craft, and so provide for the operator an attitude sense of the operating conditions existing at the controlled craft.

Another object is to providera vertical control lever and associated apparatus so that fore` and aft movement ofthe control lever will'result in a proportional angular displacement, both as to position and rate, along the pitch axis of the controlled craft.

Another object is to provide a control lever and asso.-V ciated apparatus for use in the remote control of craft movement such as aircraft ight, so that movement of the control lever to the left or right will cause a proportional bankingmovemenhboth as to position and rate of the controlled craft,and that in so doing the values of aileron, rudder and elevator movements that result from such achange will belcoordinated and so proportioned as to provide a ball-center turn.

Another object is to provide a remote control system that will supplement the inherent stability of the controlled craft obtained` by means 'of a gyro stabilization system or similar system commonly known commercially as` an automatic pilot, by means of proportional control signals which emanate from the control source and are received in the` controlled craft for conversion into suitable signals changing the control reference of the automatic pilot, resulting inthe controlled craft assuming an attitude or heading; in. accordance with the signals received from said control source.

Another object is to provide a control element where in movement of said control element will effect a cor responding movement, both in regard to angular'displacement and rate of displacement of the controlled craft.

Numerous. means have been developed heretofore to transmit proportional signals to a remotely 'located receiving station, and it is not intended that the invention` be limited in scope to use of the variable frequency. trans:- mission` system described hereinafter. Thefollowing methods are set forth as further examples of the `various possible transmission principles that may be employed for this purpose. 4,

A. Manipulation of the controlling lever mayope'rate to effect changes in the amplitude of a subcarrierof the transmitted wave, so that the amplitude is indicative of the control lever position; At. the receiver a signal may be applied to the stabilization system proportional to the amplitude, so that the attitude of the airplane corresponds with the attitude of the controlling lever of the transmitting station. B. Manipulation of the controlling lever may operate to cause a variation in the time relationship between alternate pulses, so that the duration of each,A pulse is indicative of the control lever position. At thereceiving station, the receivedpulses may be converted into voltage or current signals and applied to the stabilization system so that the attitude of the airplane corresponds with the attitude of the controlling lever.

C. Manipulation of .the controlling lever may operate to cause change in the phase of a transmitted wave, when referenced to a standardtransmitted wave, so that the phase displacement is indicative of the control lever position. At the receiving station thenphaseshift may be converted intovoltageor current signals and applied to the stabilization system, so that the attitude ofthev airplane corresponds with the attitude of the controlling lever. v

ItY is also to be understood that the radio transmission of` signals may be `replaced by applying any of the above,- enumerated methods to light or sonic signals, and that these last means of signal transmission may be more suitable for certain military applications, for example, the application of the principles of the invention to under,- water craft.

The gyro stabilized proportional control system of the invention may be defined. as a means of introducing signals to agyro stabilized craft control system, propo tional to the displacement of a remote control` element., With its proportional positioning and variable rate of application, this control system facilitates rapid attitude and throttle changes which are essential to the accom.- plishment of smooth aircraft landings.

The signals from the remote control station are im.. posed directly upon the gyroscope pick-offs demanding a response from the follow-ups which react immediately toraccomplish the ordered change. Since the signal input is directly proportional to the rate of movement of the. controls at the remote station, it follows that the gyroscopic ordered reactions will be of equivalent magni` tude. The action o-f the automatic pilot is not impaired, however, by the introduction therein of signals from the remote station and atomspheric disturbances asf sensed by the pick-up which unbalance the system will occasion a further reaction from the follow-ups. These` added signals will be induced algebraically upon the transmitted signals thus insuring maintenance of stabilized flight at` all times.

. The control lever position is indicative of the aircrafts attitude as it may be termed parallel to the Z axisV of the aircraft at all times.

,Referring to the drawingsv briefly:

Figure 1 is a schematic diagram of the Jt'ransrnittiliti;`

apparatus employed .for transmitting signals to a remote l lycontrolled object; Y s

Figure 2 is a schematic diagram of the receiving apparatus employed for receiving control signals at the remotely controlled object; I Y. 1 l w:

Figure 3 is a circuit diagram of one of the discriminator circuits vof the receiving apparatus; v

Figure 4 is a graph illustrating the output frequency characteristic of the discriminator shown in FigureY 3;

VFigure 5 is a circuitdiagram of one of the proportional converters of the receiving apparatus;l @Figure 6 is a circuit diagram illustrating the connection of the proportional converter output to an automatic pilot for aircraft elevator remote-control; and

i': Figure 7 is a circuit diagram'illustrating the connection of the proportional converter output to an automaticv pilot for aircraft rudder and aileron remote control.

Referring to 'Figure l, a controllever 1 is mechanically linked to two potentiometers 2 and 3, each controlling thefrequency of-an oscillator 4 and 5, respectively. Fore and aft movements of the control lever 1 change the oscillator 4 about its mean frequency, to effect control of pitch of the airplane. Side motion, left and right, of the control lever 1 controls the oscillator 5 about a different frequency to effect turns. Control of a third oscillator 6 bya throttle lever 7 effects changes in throttle positions. 'l The oscillator frequencies controlled by control lever position are of such frequencies that no intermodulation will occur. The oscillator frequencies are amplified in a mixing amplifier 8 and transmitted over a radio frequency'carrier wave by a transmitter 9. Switches 10, 11 and 1l key fixed frequency oscillators 13, 14 and 15, respectively, and may be used to operate auxiliary functions in the controlled aircraft, s uch as landing gear up andy down, aps up and down, etc. Theoscillators 4, 5, 6, 13, 14, and may be of any conventional design well known in the art, capable of generating audio or radio frequency electrical oscillations of different frequencies, the frequencies of which'may be varied by the potentiometers controlled' by the levers 1 and 7. It is, of course, obvious that these frequencies maybev varied by means other than variable resistors as, for example, variable capacitors or variable nductors and intheV case ofv variable nductors, these' may be supplied with magnetic cores that may be moved or displaced by the levers 1 andV 7 in order to vary the inductance of the variable inductor. 1

Referring now to Figure 2, a receiver 16 positioned in the aircraft or other mobile device to be controlled, picks up the' radio frequency carrier emitted rby the'transmitter 9v and `demodulatesv it to the original frequencies genf eratedvby the oscillators of Figure l. Currents corresponding to these frequencies are then fed through a filter and discriminator unit 17. From the discriminator unit 17 the voltages corresponding to the oscillator frequencies are applied to a proportional converter 18, which converts the voltages into signals that are applied to the desired circuits'of theautomatic pilot as will be described hereinafter more fully.

It will be observed that changes in the position of the control levers 1 and 7, Figure 1, are translated into frequency changes of channels that are,'preferably audio frequency channels although radio frequency channels may be employed if desired. These frequenciesare sent over the radio link, that is, modulated on to the carrier wave emitted by the transmitter 9, and are received by the receiving apparatus 16, the output of which Vis connected to filters 19, 20 land 21. The filters arestandard band pass lters' turned to their respective channels and passonly those frequencies to which they are turned so that they separate thefrequencies corresponding to the aforesaid oscillators. These signals are thenfed to the discriminators 22,"23 and 24,' respectively. Additional band pass filters 37, 38 and 39 are provided for theI discriminator unit 17A connected to the receiving device ssamm i n f I,

A16, being designed to pass narrow frequency bandscorresponding to the frequencies .of theoscillators 13, 14-and 15, respectively, for the purpose of separating the signals from those oscillators and applying these signals for the control of operation of the* landing gear, aps, etc. of the ard frequency modulationtype consisting of'two diode circuits 22a and 22b,` one tuned above -the mean frequency of the oscillator, for example oscillator4, by ,an amount greater than theY deviation ofthe signaLfandV the othei Vtuned below the mean frequencyl by the same amount. Figure 4 illustrates the output frequency characteristic of this circuit wherein A is the frequency characteristic of one diode circuit, for example diode circuit 22a, and B is that of the other circuit 22b. The cur-ves indicate the D.C. voltages developed across each circuit as the frequency of the signal input is varied. The D.C. voltage developed in the output circuits of the discrirninators 22, 23 and 24 are fed into the proportional converters 2S, 26 and 27 respectively, Figure 2, where they are converted into signals that are usable in the automaticpilot.

Figure 5 shows one form of a proportional converter, wherein the D.C. voltage A (Figure 3) is fed to a grid 29a of the tube 29, and the D.C., voltage B (Figure 3) is fed to a grid 28a of the tube 28. A reference A.C. voltage from the automatic pilot is impressed upon vthe grid 28b and 29b in tubes 28, and 29, respectively, so that the plate current in each tube circuit will be pulsating D.C., the amplitude `of the A.C. component of which will berlin proportion to the instantaneous D.,C. voltages being fed into the tubes by theV discriminator. The secondaries of transformers 30 and 31 are connected in series so that the voltage, induced in one is opposed by the voltageinduced in the Othr. -The resultant A.C. voltage output will be zero if both voltages from thedis criminator are-equal, butwill vary: in phasehfandamplitude as the frequency applied to the discriminator circuit is changed. This A.C.'.voltage from transformersilland 31 is fedi throughr the windings ,of potentiometerl 32 to I ground, the ,slider of which isconnectedto the grid. of the amplifying tube 33- and maybe used .as a means for calibrating the convertenfThe, output ofqthistube 33A is fed into the automatic vpilot Vsignal. circuit Ythrough transformer 34, having a resistor 34a connected across the secondary. Y Y z Figure 6 illustrates the` application of this invention to atypical automatic pilot. The attitude reference to oper- V is determined. by the direction, appears. across the output v` of winding 36. This voltage is applied to the potentiom@ eter 46 connected across the secondary of `transformer 46b. The center of potentiometer 46: is connected to one end' of the resistor-46a and this latter resistor is connected across resistor 34a, a'winding 45and potentiometer l 34b. The variablefcontactor 34al of the potentiometer 34h is connected to the resistors 38a and 38b and through these resistors to the grids 38g and 39g ofthe triodes 38 and '39 respectively. "Ihese triodes are sections of a duo-l triode vacuum tube and the plates or anodes 38p and 39p."

A of these triodes are connected to oneterminal of each of the secondary windings 38s and 39s, respectively of the transformer 3st. A Vreference,A.C.. voltage is applied to the plates 38p andv 39p from the secondaries 38s and 39s,

respectively, so that the signal applied to grids 38g and 39g will be in Vphase with the A.C. potential applied to one plate only. -If the aforesaid gust. disturbance causes a S nose-down condition, the 'signal will be in phase with plate 38p, and if it causes a nose-up condition, the signal will be in phase with plate 39p.

The other terminals of the secondaries 38s and 39s are connected to the ends of the resistor 39r and the center of this resistor is returned to the cathode circuit of the beam type amplifiers 40a and 4Gb. The common terminals of the capacitors 39m and 3911 and the capacitors 40C and 40d are connected to the center of the resistor 39A Resistor 39x is connected between the capacitors 39m and 40C and between the secondary 39s and the control grid of beam type amplifier 40a. Similiarly resistor 39z is connected between capacitors 3911 and 40d and between secondary 38s and control grid of the beam type amplifier 4Gb. yThe plate of tube 40a is connected to the solenoid 41a of the transfer valve 41 and the plate of arnplifier tube 40b is connected to the solenoid 41h, the common terminals of these solenoids 41a and 411; being connected together to the positive terminal of the anode current supply for these amplifier tubes 40a and 40b.

The amplifier tubes 49a and 40]: operate the transfer valve 41 containing the two solenoids 41a and 41b so that ifthe disturbance causes a nose-down condition, the current in solenoid 41b will be greater than the current in solenoidf41a; and if the disturbance causes a nose-up condition, the current in solenoid 41a will be greater than the curernt in solenoid 4b. The valve stem 41e is positioned by the difference in current in solenoids 41h and 41a. This valve controls the direction of flow of oil into the servo 42, so that the direction of the servo movement will depend on the direction of the disturbance. As the servo 42, linked to the elevator surface 43, moves the elevator 43 to correct for the disturbance, it also moves the rotor 44 of the pick-off device 4S, termed the fo1low-up', causing a voltage output similar to that of pick-off device 36 but of opposite phase. When the servo 42 has moved the rotor 44 until the output voltage of the winding 45 is of the same magnitude as the output of the winding 36, the currents in the solenoids 4-1b and 41a are equal and the servo 42 is stopped. As the airplane returns to level fight as a result of the displaced elevator 43, the signal output of the pick-off device 36 diminishes, the servo 42 returns to its original position, and the signal output of the pick-off device 45 diminishes.

The system just described will operate the elevator 43 to maintain level attitude during normal flying conditions. An A.C. reference voltage is applied across the potentiometer 46 by the transfermor 46b so that the pilot by manipulating the knob 47 may introduce to the signal circuit including the resistor 46a a fixed electrical signal to accomplish a fine adjustment in the attitude of the airplane. Such signals superimposed on the stabilization circuit are known as trim signals. The converter circuit of Figure 5 is included in Figure 6 to illustrate the means for introducing the proportional signals to the automatic pilot. It was shown in the discussion of Figure 5 that the voltage of the secondary of the transformer 34 is proportional in magnitude to the displacement of the control element 1 at the transmitter 9, while its phase is determined by the direction of displacement of the control element l. In Figure 6 the transformer 34 is in series with the automatic pilot signal circuit consisting of pick-off device 36, the trim potentiometer 46, the follow-up device 45, and the potentiometer 34b, so that the signal appearing on 34 causes the operation of the automatic pilot amplifier 40a- 4b, valve 4i, the servo 42, and the elevator surface 43, just as a signal arising from a disturbance. By this arrangement it is obvious that the remotely located operator may introduce trim signals to the automatic pilot just as an airborne operator could introduce tn'm signals by manipulating the knob 47. Since the signals are introduced directly into the signal channel of the control amplifer of the gyrostabilized system, the response to the control lever displacement is practically instantaneous. r[his type of system, being gyrostabilized, presents the opi 6 erator with a Aset of controls `to which he "is accustomed, without burdening him withthe responsibility of stabilizing the airplane.

Figure 7 illustrates'the application of this proportional control system having partscorresponding to lthose tillustrated in Figure 6, to the aileron and rudder vcontrols vof an automatic pilot. The aileron control consists of the pick-off device 36', mounted on the vertical axis gyro 35 in such a manner that it is sensitive to displacement `in the roll axis, and components corresponding to those described under Figure 6, which are the YtrimV potentiometer 46', phase sensitive circuit of triodes 38' and 39', amp1ifiers 40a' and 4Gb', transfer valve 41', servo 42', aileron 43', and the follow-up device 45. Thissystemoperates in a manner similar to that described for thejpi'tchcontrol, to maintain `lateral stability while the aircraft is `in* flight.

In the apparatus shown in Figure 7, thetransformer 34 connected to the `plate of amplifier tube 33"'is provided with two secondary'windings 734 and 735, instead of lone winding as shown in Figure 6, the winding'734 being'c'onnected across the `resistor 34a', the same as in Figure `6, and the winding 735 being Yconnected across the potentiometer 748. The variable portion of the lpotentiometer 748 is connected in series with the Winding 36, the winding of the follow-up device 45" and the potentiometer 34h, the variable contacter of the potentiometer `3`4b" being connected to the grids of the triodes 38 and 39" through suitable resistors. l v l The rudder control of the automatic pilot consists` of the pick-off device 36 mounted on a rate of turn 'gyro 35 so that it is sensitive to therate of change about the yaw axis. p

Y lectrical potentials from thewinding 36", the potentiometer 748, "winding 45 are applied across the potentiometer 34h" since these elements are connected in series across this potentiometer, and signals from this potentiometer are applied to the phase sensitive triodes 39"- 39 through resistors. The plates of these triodes are energized from a pair of secondaries of a transformer the same as triodes 38-39 of Figure 6. The outputs of the triodes 38"-39 are connected to the control grids of the beam type amplifier tubes 40a"40,b corresponding to tubes 40u-4Gb of Figure 6, and the outputs of these beam type amplifier tubes energize solenoids 41a"-41b to control the valve 41" and the servo 42". This system operates in a manner similar to that described for the pitch control to maintain directional stability of the aircraft in ight. The converter circuit described in Figure 5 is shown on Figure 7 as it is applied to cause coordinated turns of the aircraft proportional to control element displacement. This application differs from that described for the pitch control in that the output signal appearing across transformer 34' is applied to both aileron and rudder circuits through the use of two secondaries 734 and 735 as described. It is obvious, from'the foregoing description, that a' lateral displacement of the control element will result in the application ofV trim signals to the aileron and rudder circuits. In the aileron circuit the trim applied will cause the airplane to bank to the right or left in proportion to the control clement displacement. The signal applied to the rudder circuit will cause rudder movement until the airplane is turning at a rate proportional to the aileron trim. The potentiometer 748 is provided to permit adjustment of the proportion of the signal to be applied to the rudder circuit so as to result in a coordinated ball center turn.

While this invention has been set forth in detail with respect to a particular embodiment thereof it is not desired to limit it to the exact details described except in scope as they are defined by the following claims.

What kwe claim is:

l. A control system comprising a mobile body carrying a gyrostabilizer, a control circuit including a progressively variable element connected to said gyrostabilizer, an attitude varying mechanism controlled by said circuit, a signal receiver connected to said circuit for superimposing remote signals thereon; a signal transmitter remote from said body, a progressively variable control device connected to .said transmitter for modifying signals produced by said transmitter as a function of the magnitude of displacement of said control device from a neutral position whereby attitude lchanges of the mobile body are controlled in proportion to the magnitude of displacement of said control device from its neutral position; and circuit means provided by said signal reccivfer'for excluding remote signals from said control circuit when lsaid control device assumes its neutral position. .i v

2. A control system comprising a mobile body carrying a gyrostabilizer, a control circuitincluding a progressivelywvariable element connected to said gyr'ostabilizer, an attitude varying mechanism controlled by said circuit, a signal receiver connected to said circuit for superimposingremote signals thereon; a signal transmitter remote from said body, a progressively variable control device connected to said'transmitter for modifying signalsproduced by said transmitter as a function of the rate of displacement of said control device whereby attitudechanges of the mobile body are controlled in proportion to the rate of displacement of said control device; andf circuit means provided by said signal receiver for excluding remote signals from said control circuit when said control device assumes a neutral position.

3. A control system comprising a mobile body carrying algyrostabilizer, a control circuit including a progressively variable element connected to said gyrostabilizer, an attitude varying mechanism controlled by said circuit, la signal receiver. connected to said circuit for superimposing remote signals thereon; a signal transmitter remote 8 from said body, a progressively variable control device connected to said transmitter for modifying signals produced by said transmitter as a function of the rate and magnitude of displacement of saidV control device from a neutral position whereby attitude changes of the mobile body are controlled in proportion to the rate and magnitude of displacement of said control device from its neutral position; and circuit means provided by said signal receiver for excluding remote signals from said control circuitV when said control device assumes its neutral position.

4. A control system comprising a mobile body carrying a gyrostabilizer, a control circuit including a progressively variable element connected to said gyrostabilizer, a plurality of attitude varying mechanisms controlled by said circuit, a signal receiver connected to said circuit for superimpo-sing remote signals thereon; a signal transmitter remote from said body, a plurality of progressively variable control devices connected to said transmitter for modifying signals produced by said transmitter las a function of the magnitude of displacement of said control devices from neutral positions whereby attitude changes of the mobile body are controlled in proportion to the magnitude of displacement of said control devices from said neutral positions; and circuit means provided by said signal receiver for excluding remote signals from said lcontrol circuit when said control devices assume said neutral positions. v

ReierencesCited in the file of this patent UNITED STATES PATENTS 

